1. Field of the Invention
This invention relates to a door closer with a slide rail linkage, which door closer is capable of being concealed in a door panel or a door frame when installed. Such a door closer may have a closer shaft which can be activated by a spring in the closing direction, as well as a damping piston which interacts with this closer shaft. There may also be a pivoting actuator arm coupled to the closer shaft on one end of the actuator arm. Also, by means of a sliding block, located on the other end of the actuator arm, the actuator arm can be engaged in a slide rail, which slide rail can be installed in the other of the door frame or in the door panel.
2. Background Information
Such a door closer as described above, is shown in a publication of the Lancer Company. This type of door closer has a closer shaft with gear teeth which are engaged with a toothed rack piston, or, in other words, a piston rod with teeth. A major disadvantage of such a closer is that, on account of the use of the toothed rack, it can essentially only be used for one type of installation. Moreover, for reasons relating to the installation, the journal bearing of the closer shaft has been placed outside the housing. Thus, the overall height of the closer is relatively large, which means that the closer cannot be used in framed doors made of aluminum or steel. If door closers which are equipped with a toothed rack piston are used in connection with slide rails, these door closers produce an undesirable increasing torque at the beginning of the opening movement of the door.
This unpleasant effect results from the fact that in the interaction of the slide rail, via the mounting arm, with the toothed section of the toothed rod piston, produces an undesirably large increasing opening moment of resistance. This moment of resistance also increase steadily, thus requiring the application of a constantly increasing force by the user.
German Laid Open Patent Application No. 20 15 302 discloses a door closer which can be installed in a door frame, or can also be installed in a door. This door closer is a tubular body in which there are an axially movable closing piston and a braking piston which interacts with the closing piston. When the door is opened, the spring stretches so that the door can be closed by the force of the spring. The fluid inside the housing damps the closing movement of the door.
An alternative overhead door closer, which is connected with a slide rail, but is not configured for concealed installation is disclosed in German Laid Open Patent Application 33 45 004. This door closer has a closer shaft activated by a spring arrangement to close the door, and a damping piston connected to the closer shaft, as well as a pivoting actuator arm coupled to the closer shaft. This actuator arm is held in a guide rail by means of a slide located on the other end of the actuator arm. To improve the ease of operation of such an overhead door closer with only one actuator arm engaged in a guide rail, the closer shaft has a cam whose curved path corresponding to the opening direction of the door panel is acted on by a spring-assisted element, and whose curved path corresponding to the closing direction of the door panel is acted on by a damping piston.
All the commercially available door closers involving a slide rail installation, and suitable for installation in doors, have their journal bearing outside the housing for reasons related to the installation of the door closer. Only in that way is it possible to install the compression spring and the toothed rack in the housing. Further, the known door closer systems which have a slide rail installation are generally not suitable for installation in both door panels and door frames.